It is well documented that the elderly and post-surgical patients are at a heightened risk of falling. There are many reasons for this but, broadly speaking, these individuals are often afflicted by gait and balance disorders, weakness, dizziness, confusion, visual impairment, and postural hypotension (i.e., a sudden drop in blood pressure that causes dizziness and fainting), all of which are recognized as potential contributors to a fall. Additionally, cognitive and functional impairment, and sedating and psychoactive medications are also well recognized risk factors.
A fall places the patient at risk of various injuries including sprains, fractures, and broken bones--injuries which in some cases can be severe enough to eventually lead to a fatality. Of course, those most susceptible to falls are often those in the poorest general health and least likely to recover quickly from their injuries. In addition to the obvious physiological consequences of fall-related injuries, there are also a variety of adverse economic and legal consequences that include the actual cost of treating the victim and, in some cases, caretaker liability issues.
In the past, it has been commonplace to treat patients that are prone to falling by limiting their mobility through the use of restraints, the underlying theory being that if the patient is not free to move about, he or she will not be as likely to fall. However, research has shown that restraint-based patient treatment strategies are often more harmful than beneficial and should generally be avoided--the emphasis today being on the promotion of mobility rather than immobility. Among the more successful mobility-based strategies for fall prevention include interventions to improve patient strength and functional status, reduction of environmental hazards, and staff identification and monitoring of high-risk hospital patients and nursing home residents.
Of course, monitoring high-risk patients, as effective as that care strategy might appear to be in theory, suffers from the obvious practical disadvantage of requiring additional staff if the monitoring is to be in the form of direct observation. Thus, the trend in patient monitoring has been toward the use of electrical devices to signal changes in a patient's circumstance to a care-giver who might be located either nearby or remotely at a central monitoring facility, such as a nurse's station. The obvious advantage of an electronic monitoring arrangement is that it frees the care-giver to pursue other tasks away from the patient. Additionally, when the monitoring is done at a central facility a single nurse can monitor multiple patients which can result in decreased staffing requirements.
Generally speaking, electronic monitors work by first sensing an initial status of a patient, and then generating a signal when that status changes, e.g., he or she has sat up in bed, left the bed, risen from a chair, etc., any of which situations could pose a potential cause for concern in the case of an at-risk patient. Electronic bed and chair monitors typically use a pressure sensitive switch in combination with a separate monitor/microprocessor. In a common arrangement, a patient's weight resting on a pressure sensitive mat completes an electrical circuit, thereby signaling the presence of the patient to the microprocessor. When the weight is removed from the pressure sensitive switch, the electrical circuit is interrupted, which fact is sensed by the microprocessor. The software logic that drives the monitor is typically programmed to respond to the now-opened circuit by triggering some sort of alarm--either electronically (e.g., to the nursing station via a conventional nurse call system) or audibly (via a built-in siren). Some examples of devices that operate in this general fashion may be found in U.S. Pat. Nos. 4,484,043, 4,565,910, 5,554,835, and 5,634,760, the disclosures of which are incorporated herein by reference.
Seated at-risk patients pose a special challenge to electronic monitoring devices because they can rapidly rise to their feet, thereby quickly placing themselves in jeopardy. Since the seated patient is already postured to stand up, only a moment may be needed for a patient to rise to his or her feet and begin moving away from the chair. This situation is unlike that of the reclining patient who may first sit up and move to the edge of the bed, thereby making it easier for the staff to "catch" him or her before the bed is exited. Devices have been developed specifically for the purpose of monitoring the seated patient including, for example, the invention taught by U.S. Pat. No. 5,654,694, a battery powered unit that is designed for use on wheelchairs and cardiac chairs, the disclosure of which is incorporated herein by reference.
Of particular interest for purposes of the instant invention are those situations where the seated patient has been placed on the toilet and momentarily left unattended. Although this situation has a risk profile that is similar in many ways to that of seated wheelchair patient, the toilet presents certain unique design challenges that necessitate a different approach.
First, conventional chair occupancy monitors work by placing a pressure sensitive switch under the buttocks of the seated patient. Although this switch might take many forms, a popular arrangement is to seal together two broad bands of non-conductive material such as plastic, the inner surfaces of which have been made electrically conductive. The two plastic bands are separated by a non-conductive spacer that contains apertures therethrough which allow the conductive surfaces to come into contact if weight is placed on the unit. The patient's weight bearing down on the switch forces the two conducting faces together, thereby completing a circuit. Conversely, when the weight is lifted--i.e., when the patient leaves the monitored chair--the circuit is broken and a separate monitoring unit senses that fact and generates the appropriate alarm. Needless to say, it would just not be practical to use a chair monitor of this sort in a toilet setting, as it would be expected to interfere with the normal operation and use of the toilet.
Another design consideration in toilet seat monitors relates to the almost continuous presence of moisture around the unit. That is, it is well known to those skilled in the art that electronics and electrical equipment tend to deteriorate rapidly in the presence of moisture unless preventive steps are taken. However, a pressure switch-type monitor must necessarily be installed on or near the toilet bowl which potentially exposes it to raised atmospheric humidity levels, splashes, and other accidents that can soak the device. Finally, a monitor that is located proximate to the toilet must be made resistant to corrosive effects of common disinfectants and cleaners.
Thus, what is needed is a device that can detect a patient's presence or absence on a toilet seat and signal that condition to an electronic monitor. Additionally, this device should not interfere with the normal operation and/or use of the toilet. Finally, the device should be designed to be relatively unaffected by moisture and resistant to exposure to common cleaners and disinfectants.
Before proceeding to a description of the instant invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or preferred embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.